It's not South Sudan, Myanmar, or Iran, so...

If you had asked me if we had armed forces in that country before the the four soldiers' death in Niger became public, I definitely would have said "yes." I would not have known how many soldiers were involved or what exactly they were doing (although something related to Boko Haram and/or IQIM and/or other militants that operate in the environs of Northern Mali would have been my guess). But the question whether there were U.S. soldiers operating in Niger would have been easy just because the list of countries where the U.S. does not have a military presence is really short. The surprising thing is that U.S. Senators were not aware of the fact that the U.S. has soldiers all over the place.